In recent years, the use of wireless and RF technology has increased dramatically in portable and hand-held units. Portable RF devices have become widespread and pervasive in the consumer electronic market and their uses now include telephony, Internet e-mail, Internet video, Internet web browsers, global positioning, photography, navigation systems, in-store navigation, and linking peripherals to host devices. In fact, the number of cellular telephone subscribers alone worldwide is expected to reach 3 billion by the end of 2008, up from 2.1 billion in 2005, according to the International Telecommunication Union (ITU).
Similarly the devices incorporating wireless technology have expanded, and continue to so, including today not only cellular telephones, but Personal Digital Assistants (PDAs), laptop computers, palmtop computers, gaming consoles, wireless local area networks, wireless hubs, printers, telephone headsets, portable music players, point of sale terminals, global positioning systems, inventory control systems, and even vending machines. Whilst lagging cellular telephone subscribers today, for example 2007 consumption of wireless home devices was only approximately 134 million units, and is projected to exceed over 500 million units per annum by 2012 the overall market will likely exceed cellular telephone units as consumers procure multiple wireless devices per household.
These wireless devices interface to wireless infrastructures that can support data, voice and other services on either single or multiple standards. Typical examples of wireless standards in significant deployment today include, but are not limited to:                WiFi [ANSI/IEEE Standard 802.11];        WiMAX [IEEE Standard 802.16];        Bluetooth [IEEE Standard 802.15.1];        Industrial, Scientific and Medical (ISM) [International Telecommunications Union Recommendations 5.138, 5.150, and 5.280]; and        GSM 850/900/1800/1900 [European Telecommunications Standards Institute (ETSI)] and it's extensions General Packet Radio Service (GPRS) and Enhanced Datarates for GSM Evolution (EDGE).        
Not surprisingly, in all such consumer markets, pricing of the finished product is often a major factor in its commercial success. Moreover, as product features for portable electronic devices within each category, such as cellular telephones, become harmonized across multiple vendors greater pressure on reducing the cost of components and improving final yield arises. Accordingly, the cost pressure has led to the monolithic integration of the RF electronics to a small number of integrated circuits (ICs) incorporated onto radio boards. Typically, these ICs are manufactured using silicon for the baseband or computationally intensive elements of the signal processing and from silicon germanium, gallium arsenide, and indium phosphide for the RF circuit that forms the microwave circuit path. The microwave circuit path can be traced from the mixers upconverting/downconverting the RF signals via amplifiers, microwave filters, circulators, etc. to the RF antenna of the device. The RF circuit is also commonly referred to as a monolithic microwave integrated circuit (MMIC).
This RF circuit and the RF system it forms part of are often tested during various stages of the assembly process using conductive or operational testing to ensure the product functionality and to prevent further assembly of a non-functioning product. Clearly, further assembly of a defective subcomponent represents wasted investment and time that must be absorbed into the pricing of the non-defective units. Hence, the RF MMIC may be tested at the final stage of manufacturing of the semiconductor wafer, as a discrete MMIC after separation from the wafer, as part of the circuit board assembly of the wireless device, and/or as part of the final product testing.
In each instance, the making of an electrical connection with the MMIC may result in damage or destruction of the interface of the MMIC circuit if a severe and unintended mismatch is present. One example of such an electrical connection is plugging of an antenna into the assembly/subassembly, and conducting a radiated test of the final product. Occasionally, the act of plugging in the antenna damages or destroys the connection, resulting in an open circuit at the connector. Alternatively, the antenna receptacle itself has been damaged in some previous manufacturing operation and, unbeknownst to the test operator, the antenna will not connect properly to the sub-assembly. An open circuit presented to the output of an RF front end can result in excessive RF voltage swings brought on by the mismatch at the antenna connection. Such over-voltages can result in permanent damage to the front end, causing a reject at the final step of the assembly process where the product has its highest cost.
It would be advantageous to provide a method or circuit for reducing the damage caused or the costs incurred during manufacturing due to mismatched test coupling.